Watermarked plastic support

ABSTRACT

The invention concerns an imprintable, flexible, synthetic support bearing at least one authentication or security mark. 
     This support comprises: 
     a substrate of synthetic material 
     at least one mark on at least one face of the support and consisting of at least one layer of a composition altering the substrate opacity, 
     at least one layer of an imprintable pigment composition deposited on the face bearing the mark and optionally also on the substrate face without the mark, the mark being barely or not at all visible in reflected light and perfectly visible in transmitted light. 
     Application to the security of synthetic paper.

The present invention concerns a watermarked, printable plastic supportcontaining security markings which look like watermarks. Hereafter thesemarkings are called pseudo-watermarks.

It is commonplace to watermark paper. Paper watermarking may be carriedout in different ways depending on making "genuine" ones or artificialones called "pseudo watermarkings".

It is known that trust papers and securities comprise watermarks whichare made during the manufacture of the sheet of paper by using roundforms impressing hollowed or raised means or using watermarking rollerscomprising hollowed and/or raised drawings in association with a flatbench (Fourdrinier machine). An image is then obtained which when lookedat against the light will appear clear if the watermarking rollercomprises a raised design or dark if its design is hollowed. The clearzones arise from the thickness and the fiber density of the sheet beingless than in the areas where the watermarking roller did not print. Onthe other hand, the dark zones arise from more substantial sheetthickness and fiber density.

It is also known to make pseudo watermarks by printing or depositing acomposition, which as a rule is fatty, that shall render the sheet ofpaper permanently transparent. Transparency also may be achieved bymeans of a hot-melt substance; this substance is a polyethylene in theEuropean patent application 203,499.

A pseudo watermark may also be produced in a sheet of paper by renderingspecific zones more opaque with the use of an opaquing agent.

French patent application 2,353,676 describes a method using anopacity-controlling agent, that is one that increases the opacity, or,alternatively, decreases it.

This agent may be an aqueous suspension of a pigment or filler or asolution of a chemical compound, of a dyed compound or of a dye. Whilethe sheet is being manufactured, this agent is applied to the fiber webbefore it is removed from the wire cloth so that said agent enters theweb interstices and, following drying, shall have altered the opacity ofthe web being treated in the desired zones.

This method entails the drawback of requiring special rolling equipmentto apply this agent and the use, preferably, of a suction device tocause the agent to enter the web interstices.

This complex procedure results in non-homogeneous pseudo watermarksbecause the deposition is uneven.

U.S. Pat. No. 4,520,063 describes a synthetic-resin sheet with securitymarkings similar to watermarks. Two dyes with different rates ofmigration are applied to the sheet, the migration of thequicker-migrating dye being stopped by crosslinking due to acrosslinking agent contained in the sheet or added to the dye. Underreflected light, a pattern assuming the color of this dye will beobserved, whereas observation under transmitted light shows mixedcolors.

It is difficult to make a pseudo watermark in this manner in a plasticsheet because it requires a non-obvious selection of dyes with differingrates of migration into a specific material and it requirescrosslinking.

It may be advantageous to replace the sheet of paper with a sheet ofsynthetic material, which consists essentially of cellulose fibers forexample, in the manufacture of long lasting documents or documents whichmust withstand highly adverse handling. Such documents, for instance maybe diplomas required to last at least the life of their holders. Otherdocuments may be securities, banknotes, identification cards andpassports.

It is important that such documents bear items of authenticity, inparticular watermarks, as the paper documents do.

The watermarking techniques described above in relation to paper can beapplied only with difficulty to plastic sheets. They are particularlyinapplicable to sheets having a thermoplastic-film base.

Accordingly, one object of the invention is to create a plastic sheetwhich can be imprinted and which comprises authentication or securitymarkings that are hardly visible, or not at all, in reflected light, andwhich are perfectly visible in transmitted light.

Another object of the invention is to prevent counterfeiters or forgersfrom reproducing such authentication markings.

A third object of the invention is to provide a rapid and economicalmanufacturing method for such a sheet.

Applicants have surprisingly discovered that a sheet, in particular asheet of synthetic material, can be pseudo-watermarked by deposition of,or by imprinting, an opacity modifying composition at specific sites ofa synthetic substrate. Thereupon, this composition is covered with animprintable, pigmented layer. Remarkably, the markings so obtained arehardly or not at all visible in reflected light but are visible intransmitted light. This method is advantageously simple. Anothersignificant advantage of this method is the ability to make pseudowatermarks in several shades (graduating from light to dark, forinstance shaded); this type of watermark is more difficult to forge andcontains more authenticity data than a single-shade watermark.

Moreover, because an imprintable, pigmented layer is deposited last, themarkings so made are not easily accessible to a counterfeiter.

In the case of paper, counterfeiters make forged watermarks bydepositing a composition which alters the opacity at selected, suitablesites on the surface of a sheet of paper. In the case of the invention,which relates to a synthetic sheet, this type of forgery is impossible.In fact, if the counterfeiter were to commercially acquire a syntheticsheet coated in an imprintable manner, for instance with POLYART® fromARJOBEX Co., he would be faced with a number of alternatives.

In the first place, he may deposit an opacity-altering composition oncertain areas of the surface of such a sheet to reproduce the watermark.However, in that case, the markings so made will be quite visible inreflected light.

In the second place, the counterfeiter might dissolve the printablesurface layer of the POLYART® using a solvent and then deposit anopacity-altering composition at the desired sites, whereupon he wouldagain deposit the imprintable coating on the surface.

In the third place, the counterfeiter might acquire a synthetic sheetnot yet clad with the imprintable layer, deposit an opacity-alteringcomposition, and then deposit an imprintable surface layer.

However, all these conditions are extremely difficult to meet and properreproduction of the pseudo watermark, in particular if there are severalshades, will be impossible. The method employed to make secure a plasticsheet according to the invention is thus especially well suited to animprintable synthetic film.

Accordingly, the object of the invention is to create an imprintable,flexible, synthetic support bearing at least one security orauthentication mark, said support comprising:

a substrate of synthetic material,

at least one mark deposited or imprinted on at least one of thesubstrate faces, said mark comprising at least one composition alteringthe substrate opacity,

at least one layer of an imprintable, pigmented composition covering themark, said layer being deposited on the face bearing the mark andoptionally on the face of the substrate which lacks a mark; the markbeing hardly or not at all visible in reflected light and perfectlyvisible in transmitted light.

The mark is monochromatic or polychromatic.

The opacity-altering composition is a pigmented and/or dyed and/orfluorescent composition which can be prepared in an aqueous medium, in anon-aqueous solvent medium, or in a mixed water-solvent medium. Whenthis composition is a pigment, preferably it contains a mineral fillersuch as titanium dioxide. It may also contain colorful pigments. Thereis no restriction on the list of dyes suitable for the invention. Theopacity-altering composition comprises at least one mineral fillerand/or at least one pigmented and/or soluble dye and/or at least onefluorescing agent, at least one binder or lacquer, optionally at leastone dispersant and other additives.

Advantageously, the opacity-altering composition is a dyed and/orfluorescent ink.

Any synthetic based substrate is suitable for the invention. Preferably,a film or sheet consisting of at least one polyolefin, in particularpolyethylene or polypropylene, is used. More specifically, the syntheticbased substrate consists essentially of polyethylene that was extrudedand stretched biaxially. Advantageously, this film may have been treatedchemically or by corona discharge at its surface in order to improve itsreceptivity for the various compositions by which it is coated.

Preferably the imprintable, pigmented composition comprises a filler,which is preferably a mineral filler, at least one dispersant, at leastone binder, optionally: an insolubilizer, optionally an antistaticagent, optionally a pH regulator, and/or other additives. Such additivesfor instance may be anti-foaming agents, viscosity regulators, or waxes.

For example, such a pigment composition may be selected from thosedescribed in the British patent 2,177,413. Other formulas for improvingimprintability may be suitable. Certain compositions kill thefluorescence of the sub-layer. One of ordinary skill in the art wouldknow how to match this composition to the selected sub-layer.

The binder of the opacity-altering layer may for example be selected, innon-restrictive manner, from the following:

starches and optionally modified starches;

soy proteins;

cellulose derivatives, in particular a carboxymethyl cellulose;

alginate;

latex, especially synthetic latex, containing

styrene-butadiene copolymers, which are optionally carboxylated, and

acrylate copolymers;

polyvinyl alcohol;

vinyl resins;

epoxy resins; and

phenol-melamine resins and their mixtures.

The pigment fillers used to make the opacity-altering layer may forexample be selected from the following:

titanium oxides;

calcium carbonates;

clays;

aluminum hydroxides;

calcium sulfoaluminates (satin white);

barium sulfates (baryta white);

talcs;

kaolins;

silicas; and

silicates other than talcs and kaolins.

These fillers are fine powders (mean grain size less than 10 μm as arule). However, plastic pigments also may be used (powders ofacrylonitrile-vinylidene or polystyrene copolymers, for example).

The dyed pigments (or the pigment dyes) may for example be selected fromthe following in non-restrictive manner:

iron oxides (for instance, red, black);

chromium oxides;

phthalocyanins (blue, green);

anthraquinones (for instance violet);

quinacridones;

carbon black;

chromates of lead, of calcium, of barium, of strontium;

lead chromomolybdates;

lead sulfoselenides;

monoazoic compounds, naphthamide derivatives, naphthaorthotoluidinederivatives, acetoacetyl derivatives; and

disazoic compounds, benzidine derivatives.

Other suitable dyes are those soluble in an aqueous medium and as a ruleare divided into three categories:

the basic dyes: as a rule these are hydrochloric salts of basicdyestuffs (for instance fuchsin, malachite green); these dyes frequentlyassume azoic or triphenyl methane configurations;

the acid dyes: as a rule these are alkaline salts, in particular ofsodium or potassium, of combinations of diazoic compounds and sulfonicacid; and

the direct dyes, also called substantive dyes, which are related to theacid dyes; these are foremost sodium salts of azoic combinations withcarboxylic or sulfonic groups.

These diverse dyes and/or pigments may be in combination. It may benecessary to take into account the pH of the ultimately depositedprintable layer when selecting these dyes or pigments which may beunstable under some conditions.

A priori, any fluorescent agent is suitable, however such an agent mustbe tested because some are fluorescent only under given conditions. Itis perhaps also important that these agents be fast under visible orinvisible light depending on the use of the final product. In particularphosphorescent agents are not excluded.

The fluorescent agents may for example be selected from the followinggroup, but are not limited thereto:

the fluorescent-bleaching agents conventionally used in paper toincrease its whiteness; such may be derivatives ofdiaminostilbene-disulfonic acid, in particular derivatives of4,4'diaminostilbene-2,2'sulfonic-acid, or of nitrogenous heterocyclederivatives,

rare-earth chelates (for instance europium-doped yttrium oxysulfide) orother doped products (doped alkaline-metal fluorides, doped ferrites),zinc sulfides, or (copper activated) cadmium and zinc sulfides,

coumarin derivatives,

disulfonated B-naphthol derivatives,

disazoic derivatives,

fluorescein, eosin, and optionally mixtures thereof.

Metal, magnetic pigments of infra-red luminescent products may also beused.

Zinc-sulfide based pigments emitting at various lengths are described inthe patent applications EP A 34,059; EP A 78,538 and EP A 91,184 filedby KASEI OPTONIX.

A preferred process for manufacturing the sheet of the inventionconsists in imprinting at least once, preferably by photo-etching, atleast one face of the base plastic substrate by means of at least oneopacity-altering composition and then in coating one, or the other, orboth faces with the imprintable pigmented layer with a coating meanswhich is conventional in printing or papermaking.

Other methods for depositing the opacity-altering composition borrowedfor instance from the printing or graphic arts may be suitable also;however, photo-etching provides the most uniform and regular deposition.

To make a watermark having several shades, the opacity-alteringcomposition is deposited once or several times at selected sites overthe first deposition. The same composition or another may be used.

Other security elements may be integrated into the base film and/or intothe imprintable layer and/or into the opacity-altering composition.

The mark obtained according to the invention form a pseudo watermarkwhich also may be detected by a watermark reading and/or recognizingdevice. When the markings are fluorescent, they may be detected andobserved at the document surface using UV light.

The invention is elucidated by means of the Examples below provided inillustrative and non-limiting manner.

EXAMPLES

In the Examples below, the base plastic substrate is a biaxiallystretched film composed in the main of high-density polyethylenecommercially sold as Polyart® by ARJOBEX Co.

EXAMPLE 1

The following opacity-modifying composition is made in aqueous medium.

    ______________________________________                                        Commercial parts         by weight                                            ______________________________________                                        water                    26                                                   dispersant: aqueous solution with 50% of an                                                            0.3                                                  ammonium polyacrylate DISPEX A40                                              marketed by Allie Colloids Ltd (UK)                                           mineral filler: titanium dioxide powder                                                                39                                                   1 N sodium hydroxide     1                                                    binder: aqueous dispersion of acrylate                                                                 32                                                   copolymer with about 50% dry matter                                           marketed by BASF as ACRONAL S360D                                             insolubilizer: 30% solution of an ammonium                                                             1.1                                                  and zirconium carbonate (AZC) marketed                                        by Magnesium Electron Ltd (UK)                                                Nisrosine W Black marketed by Bayer                                                                    0.01                                                 ______________________________________                                    

This opaquing composition is deposited on a plastic film using a labphotoetching machine so as to imprint a pattern.

The film so printed is then coated on both faces with an imprintedpigment composition using an air brush; the pigment filler is a mixtureof calcined kaolin and calcium carbonate powder.

The final product is a plain pattern invisible in reflected light andvisible in transmitted light.

The product of the invention therefore is an imprintable, flexible,synthetic support comprising a pseudo watermark permitting the productto be authenticated.

EXAMPLE 2

In addition to the procedure of Example 1, an optical bleach is added tothe opaquing agent. The optical bleach is marketed as BLANKOPHOR P byBayer; it is added as 0.24 parts by commercial weight.

In this case a fluorescent pseudo watermark is achieved.

The final support may be readily authenticated in UV light.

EXAMPLE 3

The opacity-altering composition is prepared in a non-aqueous solventmedium and contains:

    ______________________________________                                                              Parts in                                                                      commercial                                                                    weight                                                  ______________________________________                                        organic solvent: ethyl acetate                                                                        21.5                                                  mineral filler: titanium dioxide powder                                                               28.5                                                  photo-etch varnish marketed by SICPA                                                                  50                                                    (Switzerland) #53575                                                          dye: black soluble dyestuff marketed by                                                               0.01                                                  MORTON CHIMIE (France) as OISOL                                               NUSIAN BT                                                                     ______________________________________                                    

The final, imprintable support is produced as in Example 1. This supportcomprises a dark pseudo watermark.

EXAMPLE 4

The opacity-altering composition is prepared in a non-aqueous solventmedium and contains:

    ______________________________________                                                             Parts by                                                                      commerical                                                                    weight                                                   ______________________________________                                        an organic solvent: methylethyl ketone                                                               30                                                     a white ink for photo-etching: SIPCA                                                                 110                                                    #60498                                                                        a yellow fluorescent pigment marketed                                                                 2                                                     by HOECHST as LUMILUX                                                         ______________________________________                                    

A final, imprintable support is produced as in Example 1. The support isauthenticatable by a fluorescent pseudo watermark.

EXAMPLE 5

Example 1 is repeated, and a violet dye VISCOFIL 4 RL PATE marketed bySANDOZ is added to the opaquing agent in the amount of 0.08 parts bycommercial weight.

A colored pseudo watermark is obtained.

EXAMPLE 6

The opaquing composition of Example 1 is reproduced, with substitutionof the black dye by a green UNIPERSE GP dye marketed by CIBA GEIGY. 0.32parts by commercial weight are added.

A first pattern is deposited using a spray gun. The opaquing compositionis deposited on part of this pattern, using the spray gun again.

Finally, the imprintable, pigmented layer is deposited as in Example 1.

A colored pseudo watermark is obtained, comprising a light and a darkerpart; this watermark therefore comprises two shades.

We claim:
 1. An imprintable, flexible synthetic support bearing at leastone authentication or security mark, said support comprising:a substrateof synthetic material, at least one mark deposited or imprinted on atleast one face of the substrate, said mark comprising at least onecomposition altering the substrate opacity, at least one layer of animprintable pigment composition covering the mark, said layer beingdeposited on the face with the mark and optionally on the face of thesubstrate without marking, the mark being barely visible in reflectedlight and perfectly visible in transmitted light.
 2. Support accordingto claim 1, wherein the marking is monochromatic or polychromatic. 3.Support according to claim 1, wherein the opacity-altering compositioncontains at least one mineral filler and at least one binder.
 4. Supportaccording to claim 1, wherein the opacity-altering composition containsat least one soluble dye or a pigment colorant.
 5. Support according toclaim 1, wherein the opacity-altering composition contains a fluorescingagent.
 6. Support according to claim 1, wherein the opacity-alteringcomposition is a dyed or fluorescent ink.
 7. Support according to claim1, wherein the synthetic substrate is a film or a sheet composed of atleast one polyolefin.
 8. Support according to claim 7, wherein thepolyolefin is polyethylene or polypropylene.
 9. Support according toclaim 7, wherein the substrate consists essentially of high-densitypolyethylene, is formed by extrusion, is biaxially stretched and isoptionally surface-treated with corona discharges.
 10. Support accordingto claim 1, wherein the imprintable pigment composition comprises amineral filler, at least one dispersant, at least one binder, optionallyan insolubilizer, optionally an anti-static agent, and optionally a pHregulating agent.
 11. A method of manufacturing a support according toclaim 1, wherein at least one opacity-altering composition is depositedat specific sites on at least one of the faces of the syntheticsubstrate to form at least one authentication or security mark andwherein an imprintable, pigmented layer is deposited on the face withthe mark and optionally also on the other side.
 12. Method according toclaim 11, characterized in that the opacity altering composition isdeposited by photo-etching.
 13. Method according to claim 11, whereinthe imprintable pigmented layer has a dry specific weight between 5 and30 g/m² and preferably about 10 g/m².